Electrostatic imaging



March 3, 1970 KOLIBAS ETAL 3,498,712

ELECTROSTATIC IMAGING 4 Sheets-Sheet 1 Filed April 5, 1967 INVENTORS.

JAMES A. A a/64.5

D/I/PM/V 6i man s5? JOHN S. COPELAND BY 1 S ATTORNE Y March 3, 1970 KOLIBAS ETAL 4 Sheets-Sheet 2 INVENTORS.

JAMES A. KOL/BAS DARWIN S. CROUSER JOHN S. COPELAND ATTORNEY March 3, 19 70 J KOLJB'ASI ETAL 3,498,712

ELECTROSTATIC: IMAGING Filed Aprii 5, 19s? 4 Sheets-Sheet 25 SS Zfi w WA N NMOL V R E E 0 V CW?T WS MJYM Rm mw March 3, 1970 'J. A. KOLIBAS ETA!- 3,493,712

ELECTROSTATIC IMAGING Filed April 5, 19s? 4 Sheets-Sheet 4 INVENTORS.

JAMES 4. KOL/BAS DARK IN 5. CROUSER JOHN S. COPELAND ATTORNEY United States Patent Office 3,498,712 Patented Mar. 3, 1970 3,498,712 ELECTROSTATIC IMAGING James A. Kolibas, Cleveland, Darwin S. Crouser, Mentor, and John S. Copeland, Chagrin Falls, Ohio, assignors to Addressograph Multigraph Corporation, Cleveland, o

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Filed Apr. 3, 1967, Ser. No. 627,757 Int. Cl. G03b 27/34, 27/40, 27/70 US. Cl. 355-57 9 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Devices such as Patent 3,180,239 make possible the imaging of a photosensitive sheet directly from material to be copied. All such devices known to the art have certain practical limitations which this invention eliminates. The size of the usual direct copy device is greater than normally acceptable for general ofiice use or even in the smaller printing establishments.

Hence, this invention may be classed with the above patent in general nature and purpose with the object of providing an improved low profile and ability to accommodate a variety of photosensitive sheet sizes together with the ability to enlarge and reduce from the original material to the image and to spot the image on the selected sheet where desired.

SUMMARY OF THE INVENTION Discovery that a Peaucellier mechanism can be devised with one variable incorporating a fixed distance, and the employment of that fixed distance to establish an image plane related to an object plane, and relating that discovery to the mechanical concept of delivering a photosensitive sheet along the plane where the image is located, regardless of where it is caused to fall; and the processing of an exposed sheet.

DESCRIPTION OF THE DRAWING FIGURE 1 is a schematic side elevation of a production machine embodying the principles of the invention.

FIGURE 2 is a top plan view, to a larger scale, as viewed substantially along the line 2-2 of FIGURE 1.

FIGURE 3 is an elevation view to an enlarged scale of the lens focusing apparatus, shown in FIGURE 1.

FIGURE 4 is a section view taken along the line 4-4 of FIGURE 2.

FIGURE 5 is a broken section of the master conveyor to an enlarged scale as viewed along the line 55 of FIGURE 1.

FIGURE 6 is a fragmentary portion of the surface of the conveyor of FIGURE 5, as viewed along the line 6-6 of FIGURE 5.

FIGURE 7 is a schematic illustration of the lens carriage system as positioned for maximum reduction of the object material.

FIGURE 8 is the lens system position for a one-to-one ratio of the object material.

FIGURE 9 is a view of the lens system in the position for maximum enlargement of the object material.

DESCRIPTION OF THE PREFERRED EMBODIMENT A composition shuttle 10, sometimes referred to in the art as a copyboard, is provided for the purpose of accepting original material to be copied. It is termed a composition shuttle because the first position is table-like in order that the material may be arranged in proper relationship on the table for the desired image to be made upon a resultant photosensitive sheet, such as a master for lithography. On occasion, several pieces of material will be grouped together and thereby composed to set up a resultant image for the final impression to be made upon a master.

The illustrated apparatus, and the technical principles set forth hereafter, are applicable to any photosensitive sheet. One outstanding use for the apparatus is the rapid and superior production of masters for lithographic use. Therefore, the term master is used herein as a specific example of a photosensitive sheet.

The composition shuttle has a support surface 11 upon Which original material is placed and composed or related in order to be prepared for presentation to the camera. The shuttle is supported by mechanism, which is not illustrated in these drawings, for causing the shuttle to move to a second position as shown in phantom outline. In the second position, the material is placed on a second support plane 12. The preferred embodiment incorporates a transparent plate glass reference support plane 12 and the shuttle carries the original material downwardly and forwardly from its uppermost position shown in full lines in FIGURE 1, to the vertical contact position of the second support plane 12. A manual handle 13 is shown as the means to drive the mechanism for causing the shuttle 10 to move between the table position and the vertical contact position.

On the opposite side of the plane 12 from the contact position, is a lamp house 15 in which a plurality of lamps 16 are placed to illuminate the subject matter held between the support plane 12 and the surface 11 of the shuttle 10.

A bellows 18 with a lens 19 permits only the light of a projected image to emerge. The illustration in FIGURE 1 is schematic but represents an actual working device. The literal structure is eliminated in order to bring forth only those cooperating parts which are necessary for an understanding of the novel new structure which has been proven of value. The entire device is housed in a conven tional covering which enables the interior of the machine to be kept at a substantially dark condition.

The illustrated embodiment of the invention is built around a novel concept developed from the original Peaucellier effect. The mechanism and its various uses, including the design of an autofocuser is known. It will be observed that the phenomena of the autofocuser is built upon the premise of the object-to-lens and lens-toimage distances being two constantly variable conditions properly related to produce sharp focus throughout a range of size projection.

For full understanding of the invention, it is necessary to observe the interrelation of several factors centered about the Peaucellier principles which produce, in their totality, a desirable new invention.

First, for the making of planographic master sheets, a projected literal image, not a reversal, is usually required. Such image is referred to as right reading in the art. To project a right reading image, an uneven number of mirrors is employed. A lens inverts and reverts the image. One or an uneven number of mirrors, will revert the image to a right reading form.

Secondly, in order to reduce the total bulk of the equipment for projecting and processing, the copy-board places the object on plane 12 below the composition table height. The optical axis of lens 19 is, therefore, caused to be at a lower level. Then, a mirror is used to revert the image, and to project the image upwardly so that processing equipment may be stacked over the lens system without creating an unduly long or high structure.

The use of a Peaucellier autofocus is based on a theoretical lens having one nodal point but in actual com- .mercial lenses there are two nodal points, and they are separated from one another. Further, in a commercial series of lenses, no two are likely to be exactly alike. Hence, a commercial production of machines based upon such variable components normally introduces need for expensive custom design for each machine.

- It was discovered that the use of the mirror makes focusing sure and simple. The image plane to which the im age is projected is at 90 to the plane 12. Thus, by setting the lens-to-object distance close to its calculated proper distance, the lens-to-mirror distance may then be obtained empirically because the image may move along the perpendicular image plane over a wide range of field. The unexposed master is caused to stop where the image is properly located. This avoids complex structures which attempt to focus on a fixed exposure station. All that is required is compensation for manufacturing tolerances.

The autofocus device as set forth in the drawings includes first and second links 21 and 22 with a third link 23 therebetween. The links are all united at a common movable attachment point 25, and the link 21 is secured to the frame of the machine at a fixed support pivot 27.

A flat rail 29 on one side of the machine, as seen best in FIGURE 2, and a rod rail 30 on the opposite side of the machine, provide a locating and transport track for a carriage 32 which carries a mirror 33. The flat rail 29 supports a non-confined wheel 34 as shown best in FIG- URE 4, whereas rod rail 30 carries closely fitted precision bearing members. The carriage 32 bridges between the rails. Thus, the rod 30 provides a fixed reference, and expansion and contraction due to thermal variances will be compensated in the wheel 34 which is free to shift. This construction confines expansion and contraction to be effective from one fixed reference.

Lens carriage 35 on the link 23 carries the lens 19 and the bellows 18 through advance and retract focusing movements.

The structure as thus far described is arranged such that movement of the lens carriage 35 will cause the mirror carriage 32 to move in an exact relationship which is predictable throughout all directions and degree of movement of the carriage 35.

In order to compensate for manufacturing tolerances, the three links are provided with a telescopic adjustment 38 on the link 21, adjustment 39 on the links 22, and adjustment 40 on the link 23.

The usual autofocus device places an image plane parallel to the subject plane. The present invention provides for the image to be projected upwardly from the optical axis to a plane perpendicular to the support plane 12. A belt carriage 41 provides a means for carrying a blank potential master into position on that plane to be exposed by the lens system.

A lithographic master useful with this invention is a sheet having a surface which is capable of holding an electrostatic charge in the dark. When exposed to light, the surface becomes conductive where the light strikes. The charge in the conductive area is then neutralized by opposite charges on the back of the sheet. The area not discharged remains as a latent electrostatic image of the projected object being reproduced. The charges thus arranged in image fashion will attract properly prepared fusable material which is thereafter fused to make a permanent image.

In conventional practice, the unexposed and properly charged blank master is placed face-up on a support. In

order to carry out the objects of this invention wherein the entire apparatus is kept within practical space limits, the optical axis is placed low and projected upwardly to an exposure station on the image plane. A bank charged master is carried face down to the exposure station by the belt carriage 41.

Refer to FIGURE 5. FIGURE 5 is only a portion of a section through the carriage 41, but it is greatly enlarged to illustrate the structure and principle. The structure is not set forth in the schematic FIGURE 1. The FIGURE 5 illustration is one practical embodiment of a means to transport blank masters, and is recommended. It is formed of a vacuum chamber housing 42 having a perforated bottom wall 43 over which endless belts 44 travel. In FIGURE 1, it is seen that the opposite ends of the carriage 41 are provided with rollers. The belts 44 on the top and bottom opposed surfaces of the chamber housing 42 are represented in the single line drawing of FIG- URE 1. The belts 44 are spaced in order that not all of the perforations in wall 43 are closed by the belts. A sheet master fed to the area of the bottom wall 43 will be held.

along with belts 44 by differential pressure and gently moved into an exposure position by the belts. A controllable drive means 45 provides power to move the belts 44 around the housing to pick up a blank master, move that master to its exposure position where it is held stationary until exposed, and then transport the exposed master to a development station. The arrows in FIGURE 5 indicate a flow of air. A blower connected into the housing 42 will draw sufficient air through the perforations of the wall 43 to create the necessary pressure differential. An extreme low pressure is unnecessary because the large area of the master will produce suflicient holding force from a low differential pressure to carry the relatively light weight of a sheet of master material.

In FIGURE 1, the masters are shown as being positioned in a stack 46 ready for delivery to the belt carriage 41. Storage bins 47 and 48 hold masters of various sizes ready for substitution in the stack 46 as desired. This apparatus will successfully expose any size masters within the design limits of the machine. For example, a practical embodiment will include the limits of a 9 x 12 up to a 15 x 18 master. Any size master within these limits can then be fed through the device and properly located and exposed by the equipment illustrated and described.

A feeding mechanism 49, which is shown in FIGURE 1 as a pair of rollers symbolizing a sheet feed type, will cause a top sheet from the stack 46 to move through an electrostatic charger 50 before being placed in position to be attracted to the perforated wall 43.

If the device of this invention were intended to expose one size master from one size and location of original copy, then the master would be caused to move out along the belt carriage 41 a fixed distance, and that distance would be related to the position of the image which would come through the lens system. However, the object of this invention is to provide an apparatus which will enable the original material to be enlarged or reduced in size, and to be placed with respect to a particular master such that the information from the original material may be located in any desired location upon the surface of the master.

Accordingly, the lens system is designed such that the optical center picks up the center of the available space for placement of original material against the support plane 12. This is the optical field. The optical center of this area is then projected upon the belt carriage 41. The original material may be placed around the optical field area and thus be positioned in a selected area of the exposed master. Further, as the projected image is caused to be enlarged or reduced in size, or projected at a one-to-one ratio, the lens and mirror will move in relationship to one another and the optical center will be projected into a different area of the belt carriage 41 for each selected size ratio. For this reason, the station to which the blank master moves cannot remain fixed upon the belt carriage 41, but must move along with the position of the mirror 33. Furthermore, regardless of the size master being employed, this device always places the center of that master upon the optical center regardless of where the optical center is positioned. Therefore, long masters must be placed such that the leading edge of the master is a further distance with respect to the optical center than the smaller masters.

Positioning of the masters in particular exposure stations upon the belt carriage 41 is accomplished by providing a pair of rod rails 52 carried by the mirror carriage 32. Rod rails '52 are parallel to the surface of the belt carriage 41. A probe carriage 53 mounted on the rod rails 52 carries a sensitive switch and feeler 54. The feeler of the switch 54 projects upwardly between the belts 44. The belts 44 may run indefinitely if there is no master carried on the bottom wall 43, but whenever a master is caused to be carried'by'the carriage, it will eventually intercept the feeler of the switch 54. The switch 54 iselectrically connected, although not illustrated so in the drawing, to stop the drive means 45 instantaneously upon contact with the feeler of switch 54.

The probe carriage 53 is shiftable upon the rod rails 52 by means of a manually operable flexible cable 55 which leads to the console of the exposure device. Preferably the manual control is located adjacent the stack 46 in order that it may be conveniently changed whenever the length of master is changed. A short master will dictate movement of the probe carriage 53 to a position close to the mirror carriage 32, whereas the longer masters will dictate a movement away from the carriage 32. Because the switch 54 is carried with the mirror carriage 32, the lead edge of any master traveling the carriage 41 will come to a halt in the same relationship to the optical center as reflected by the mirror 33 regardless of what degree of magnification is selected by the autofocus device. Furthermore, the lead edge of the master will always project beyond the optical center the same distance regardless of the magnification setting. Therefore, arrangement of original material around the optical center of the optical field on support plane 12 may accurately predict the resultant location of the material on the master regardless of What size master is exposed.

In order to change the image-to-object ratio through the optical system, the lens carriage 35 is driven by a cable drive system '58. This system is not included in the FIGURE 1 in order to avoid confusion in that drawing, but may be seen in the FIGURES 2 and 3. Refer particularly to FIGURE 3 wherein it is seen that the cable is guided around an extreme end pulley 59. Two pulleys 60 and 61 are representative of a guide series of pulleys which enables the cable to extend to the console area of the apparatus where it is readily accessible to the operator. A manual control on the cable with an index is employed to enable the operator to know precisely where the lens carriage 35 is positioned. Preferably, the marking system is arranged to indicate magnification for a particular setting rather than actual physical position.

The FIGURES 7 through 9 indicate the manner in which the links follow the movement of the lens carriage as it moves either forward or backward to the FIG- URES 7 and 9 position from the central FIGURE 8 position. According to the proven Peaucellier principles, the FIGURE 8 position produces a one-to-one projection ratio between object and image. Any movement from this central position wherein the links define a 45 triangular relationship will cause a change in image size. In order to change image size, the mirror moves with respect to the fixed support pivot 27, and thus necessitates the change in the master location in order to keep the center of the master on the optical center as reflected by themirror.

The device of this invention contemplates modular construction with maximum operator convenience. A developing unit 64 is positioned to receive an exposed master from the belt carriage 41. Control mechanism which is not illustrated, causes the belt carriage 41 to advance the exposed master by overriding the control of switch feeler 54. The exposed master is delivered to the toner unit 64 and there a fusable toner material is caused to adhere to the electrostaatic charge remaining on the surface of the master, according to well-known electrostatic imaging procedures.

A reversal guide and drive system 66 will cause a master emerging from the unit 64 to invert and return in direction toward the composition shuttle 10 at the far end of the machine. It is within the contemplation of this invention, however, to provide a rear opening whereby some special type masters, such for example as photographically developed silver halide masters, may be removed wet from the rear portion of the machine.

A conveyor 68 accepts the inverted master from the reversal guide 66 and carries the unfused but toned imaged master to a correction station 70. The conveyor is similar to the belt carriage 41 in that it is composed of a plurality of belts, and a probe of sensitive switch 72 projects between these belts to intercept a master as it progresses across the correction station. The switch 72 is included in a circuit which will cause the drive of the conveyor 68 to stop if programmed for master inspection. When the master is brought to a halt at the correction station, it may be lifted from the conveyor and undesired toner physically removed by gentle brushing. By this means, unwanted stray toner may be removed, or entire areas may be removed quickly and efiiciently. Thus, less preparation is necessary for the original material, knowing that unwanted portions may be easily removed.

After the master is corrected, it is placed back on the conveyor 68, and the control of switch 72 is overridden to cause the corrected master to proceed through a fuser zone 75 where the toner is caused to adhere permanently to the surface of the master, and thereafter be delivered along conveyor 78 to a delivery station 100.

Whereas the present invention has been shown and described herein in what is conceived to be the best mode contemplated, it is recognized that departures may be made therefrom within the scope of the invention which is, therefore, not to be limited to the details disclosed herein, but is to be afforded the full scope of the invention as hereinafter claimed.

What is claimed is:

1. An apparatus for photo exposure wherein a document to be reproduced is placed in a first support plane, and an unexposed photosensitive sheet is placed in a second support plane perpendicular to said first plane, comprising:

first, second and third links joined at a common attachment point pivot junction;

each link having a second attachment point a distance from said common pivot junction, one attachment point of one of said links secured by a support pivot, and means for confining the links to move the second attachment point of each relatively along a straight line extending perpendicular to said first plane;

a mirror carriage with a mirror carried by said second link, and a lens carriage with a lens mounted thereon carried by said third link, said second and third links arranged to project an image through said lens and mirror from said first support plane to said second support plane;

said carriages related through said links to provide an image on said second planein a selected range and size relationship from less than the size of the object original to more than the size of the object original and in sharp focus throughout an infinite number of intermediate positions within said range, each size requiring its particular angular relationship of said links and its unique position along said second support plane as a consequence; transport means for moving said unexposed photosensitive sheet along in said second plane a predetermined finite distance unique to a given projection; and

means movable as a function of relative link movement for locating a sheet densing device along said second plane in a position always adjacent the mirror-projected image position, said sheet sensing devicebeing in control of said transport means to bring a sheet to a stop in a position of registration with the position of said projected image.

2. In apparatus as defined in claim 1, a rail for said mirror and lens carriages, said rail holding said carriages to movement parallel to said second support plane.

3. In apparatus as defined in claim 1, means to drive said lens carriage along said rail to predetermined station positions for causing a selected projection image size, said second link moving by reaction drive through said common attachment and retaining accurate focus at all stations.

4. In apparatus as defined in claim 1, said transport movable in a path along the direction of mirror carriage movement to carry sheets in said second support plane, said transport having a place of transport beginning adjacent said first support plane;

sensing means carried with said mirror for sensing arrival of a sheet to a stop position as it is carried on said transport; and

drive means for said transport, said drive means having a starting control to commence transport movement, and said sensing means being a stop control to cause said drive means to stop said transport upon arrival of a sheet.

5. In apparatus as defined in claim 4, the provision of means to extend and retract the sensing means, relative to the mirror, along the path of transport movement, for setting the stop position according to the length of the photosensitive sheet, whereby a selected length of sheet may be placed into the image area reflected by the mirror wherever the image may fall along said path.

6. Apparatus for making an exposure on a photosensitive sheet, comprising in combination:

a composition shuttle copyboard having a table surface,

and means for moving said surface between a composition layout position at table height and a lower vertical object exposure plane;

optical system means for projecting an image from said object exposure plane upwardly to an image plane located perpendicular to said vertical object exposure plane; and

transport means for:

(1) delivering a photosensitive sheet into exposure position on said image plane supported photosensitive side down;

(2) causing said sheet to dwell during exposure;

and

(3) thereafter removing said sheet from said exposure position. v

7. An apparatus for making an exposure on a photosensitive sheet, as defined in claim 6, further characterized in that:

a settable selector means for indicating the size photosensitive sheet to be used;

a sensing switch movable along said image plane as a function of setting said selector means, said sensing switch in control of said transport means for causing said sheet to stop at a position selected by said selector means; and said optical system means being a variable magnification device to size and focus an image on said object exposure plane according to the selected stopping position.

. 8. In apparatus as defined in claim 6, a processing station toner device for supply of electrostatic toner to an imaged sheet passing face down;

said means for step (3) causing said sheet to pass through said processing station; and 1 means to reverse the sheet travel direction and direct the sheet toward said shuttle,

an availability station wherein said image developed sheet is accessible to the operator for inspection and alteration; and

a fusion station to fix the toner as a fixed image.

9. An apparatus for .photo exposure wherein a document to be reproduced is placed in a first support plane, and an unexposed photosensitive sheet is placed in a second support plane perpendicular to said first plane, compl'lSlllg;

an auto-focus device including means for projecting an image from said first plane along said second plane and means to turn said image in focus toward said second plane, said auto-focus device producing an infinite variation in size of said projected image within a given range with each size projection falling in a unique station position along saidsecond plane; transport means for delivering a photosensitive sheet into exposure position on said image plane supported photosensitive side positioned to receive said image; means movable as a function of auto-focus device operation for locating a sheet sensing device along said second plane in a position always adjacent the projected image position, said sheet sensing device being in control of said transport means to bring a sheet to a stop in a position of registration with the position of said projected image; and means for reactivating said transport means after the exposure for removing such sheet from said exposure position.

References Cited UNITED STATES PATENTS 1,103,343 7/1914 Becker 355--56 1,404,440 1/ 1922 Jobke. 2,168,190 8/1939 Busse 35572 3,397,627 8/1968 Bruning 355-10 NORTON ANSHER, Primary Examiner L. H. MCCORMICK, JR., Assistant Examiner US. Cl. X.R. 3s5 10, 66, 74 

